I'm getting ready to officially pull the trigger on a 2006 Triton TR21X with a 2007 250hp Optimax Pro XS. She's at a dealer getting a complete overhaul (carpet, seats, accessories, motor, gel coat, wiring, trailer lining, odds and ends, etc.) The hull is in perfect shape, and after the upgrades it will essentially be a new boat (I'm told). I don't own it yet, so I don't have the serial number for the motor, so apologies.
In the meantime, I've been hunting around for some things I plan to add to the boat once I get it and I have stumbled into a battery conundrum.
I want to cut down on wires and weight, so I ordered some "Marine" LiFePO4 batteries from a well-respected company in China - a 36v 100ah battery pack and a 12v 200ah battery. The 36v 100ah pack will be for a 112 Ultrex, and I *hope* that the 12v 200ah battery will be used as the cranking battery and run all of my electronics.
My question is this:
If, for some reason, the 12v 200ah battery will not crank the Optimax (Slight language/terminology barrier with my contact, and even though she assured me it would work, I'm concerned that the battery's internal BMS may limit max AMPs below what's needed), what is the best option for a dedicated cranking battery? This battery would do NOTHING other than crank the engine, and would be hooked up to the alternator for recharging while running.
I have looked at the "Batteries That Meet The Requirements" page, and understand the 800cca/1000mca that are required by the Opti's, but I *think* that those requirements are listed under the assumption that the cranking battery will also be used to power other electronics in the boat...right? I also realize that the battery meets the 180ah requirement, but, again, with the internal BMS I am worried about a "governor" so-to-speak.
If the only job of a battery is to crank the motor, get recharged, and do it again, what is the smallest/lightest battery I could get away with for that application?
Appreciate any feedback. Thanks.